Leadless cardiac pacing devices

ABSTRACT

Implantable leadless pacing devices and medical device systems including an implantable leadless pacing device are disclosed. An example implantable leadless pacing device may include a pacing capsule. The pacing capsule may include a housing. The housing may have a proximal region and a distal region. A first electrode may be disposed along the distal region. One or more anchoring members may be coupled to the distal region. The anchoring members may each include a region with a compound curve.

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims priority to U.S. Provisional Application No.61/866,799 filed on Aug. 16, 2013, the entire contents of which ishereby incorporated by reference.

TECHNICAL FIELD

The present disclosure pertains to medical devices, and methods formanufacturing medical devices. More particularly, the present disclosurepertains to leadless cardiac pacing devices.

BACKGROUND

A wide variety of medical devices have been developed for medical use,for example, cardiac use. Some of these devices include catheters,leads, pacemakers, and the like. These devices are manufactured by anyone of a variety of different manufacturing methods and may be usedaccording to any one of a variety of methods. Of the known medicaldevices and methods, each has certain advantages and disadvantages.There is an ongoing need to provide alternative medical devices as wellas alternative methods for manufacturing and using medical devices.

BRIEF SUMMARY

This disclosure provides design, material, manufacturing method, and usealternatives for medical devices. An example medical device may includean implantable leadless pacing device. The implantable leadless pacingdevice may include a pacing capsule. The pacing capsule may include ahousing. The housing may have a proximal region and a distal region. Afirst electrode may be disposed along the distal region. One or moreanchoring members may be coupled to the distal region. The anchoringmembers may each include a region with a compound curve.

An implantable leadless pacing device system may include a deliverycatheter having a proximal region, a distal holding section, and a lumenformed therein. A push member may be slidably disposed within the lumen.A leadless pacing device may be slidably received within the distalholding section. The leadless pacing device may include a housing havinga proximal region and a distal region. A first electrode may be disposedalong the distal region. A plurality of anchoring members including afirst anchoring member may be coupled to the distal region. The firstanchoring member may be capable of shifting between a firstconfiguration when the leadless pacing device is disposed within thedistal holding section and a second configuration when the leadlesspacing device is advanced out from the distal holding section. Thedistal holding section may have a longitudinal axis. The first anchoringmember may be arranged substantially parallel with the longitudinal axiswhen the first anchoring member is in the first configuration. The firstanchoring member may include a region with a compound curve when thefirst anchoring member is in the second configuration.

Another example implantable leadless pacing device system may include adelivery catheter having a proximal region, a distal holding section,and a lumen formed therein. A push member may be slidably disposedwithin the lumen. A leadless pacing device may be slidably receivedwithin the distal holding section. The leadless pacing device mayinclude a housing having a proximal region and a distal region. A firstelectrode may be disposed along the distal region. A plurality ofanchoring members including a first anchoring member may be coupled tothe distal region. The first anchoring member may be capable of shiftingbetween a first configuration when the leadless pacing device isdisposed within the distal holding section and a second configurationwhen the leadless pacing device is advanced out from the distal holdingsection. A contact section of the first anchoring member may contact aninner wall surface of the distal holding section when the firstanchoring member is in the first configuration. The contact section maybe positioned proximally of a distal end of the first anchoring member.The first anchoring member may include a region with a compound curvewhen the first anchoring member is in the second configuration.

The above summary of some embodiments is not intended to describe eachdisclosed embodiment or every implementation of the present disclosure.The Figures, and Detailed Description, which follow, more particularlyexemplify these embodiments.

BRIEF DESCRIPTION OF THE DRAWINGS

The disclosure may be more completely understood in consideration of thefollowing detailed description in connection with the accompanyingdrawings, in which:

FIG. 1 is a plan view of an example leadless pacing device implantedwithin a heart;

FIG. 2 is a perspective view of an example leadless pacing device;

FIG. 3A is a cross-sectional view taken through line 3A-3A;

FIG. 3B is an alternative cross-sectional view;

FIG. 3C is an alternative cross-sectional view;

FIG. 4 is a partial cross-sectional side view of an example medicaldevice system positioned adjacent to a cardiac tissue;

FIG. 5 is a partial cross-sectional side view of an example leadlesspacing device attached to a cardiac tissue;

FIG. 6 is a partial cross-sectional side view of another example medicaldevice system positioned adjacent to a cardiac tissue; and

FIG. 7 is a partial cross-sectional side view of another example medicaldevice system positioned adjacent to a cardiac tissue.

While the disclosure is amenable to various modifications andalternative forms, specifics thereof have been shown by way of examplein the drawings and will be described in detail. It should beunderstood, however, that the intention is not to limit the invention tothe particular embodiments described. On the contrary, the intention isto cover all modifications, equivalents, and alternatives falling withinthe spirit and scope of the disclosure.

DETAILED DESCRIPTION

For the following defined terms, these definitions shall be applied,unless a different definition is given in the claims or elsewhere inthis specification.

All numeric values are herein assumed to be modified by the term“about,” whether or not explicitly indicated. The term “about” generallyrefers to a range of numbers that one of skill in the art would considerequivalent to the recited value (i.e., having the same function orresult). In many instances, the terms “about” may include numbers thatare rounded to the nearest significant figure.

The recitation of numerical ranges by endpoints includes all numberswithin that range (e.g. 1 to 5 includes 1, 1.5, 2, 2.75, 3, 3.80, 4, and5).

As used in this specification and the appended claims, the singularforms “a”, “an”, and “the” include plural referents unless the contentclearly dictates otherwise. As used in this specification and theappended claims, the term “or” is generally employed in its senseincluding “and/or” unless the content clearly dictates otherwise.

It is noted that references in the specification to “an embodiment”,“some embodiments”, “other embodiments”, etc., indicate that theembodiment described may include one or more particular features,structures, and/or characteristics. However, such recitations do notnecessarily mean that all embodiments include the particular features,structures, and/or characteristics. Additionally, when particularfeatures, structures, and/or characteristics are described in connectionwith one embodiment, it should be understood that such features,structures, and/or characteristics may also be used connection withother embodiments whether or not explicitly described unless clearlystated to the contrary.

The following detailed description should be read with reference to thedrawings in which similar elements in different drawings are numberedthe same. The drawings, which are not necessarily to scale, depictillustrative embodiments and are not intended to limit the scope of theinvention.

Cardiac pacemakers provide electrical stimulation to heart tissue tocause the heart to contract and thus pump blood through the vascularsystem. Conventional pacemakers typically include an electrical leadthat extends from a pulse generator implanted subcutaneously orsub-muscularly to an electrode positioned adjacent the inside or outsidewall of the cardiac chamber. As an alternative to conventionalpacemakers, self-contained or leadless cardiac pacemakers have beenproposed. A leadless cardiac pacemaker may take the form of a relativelysmall capsule that may be fixed to an intracardiac implant site in acardiac chamber. It can be readily appreciated that the implantation ofa leadless pacing device within a beating heart could become dislodgedas the heart functions. Accordingly, it may be desirable for a leadlesspacing device to include an anchoring mechanism and/or one or moreanchoring members to help securing the pacing device to the heart.

FIG. 1 illustrates an example implantable leadless cardiac pacing device10 implanted in a chamber of a heart H such as, for example, the rightventricle RV. Device 10 may include a shell or housing 12 having adistal region 14 and a proximal region 16. One or more anchoring members18 may be disposed adjacent to distal region 14. Anchoring members 18may be used to attach device 10 to a tissue wall of the heart H, orotherwise anchor implantable device 10 to the anatomy of the patient. Adocking member 20 may be disposed adjacent to proximal region 16 ofhousing 12. Docking member 20 may be utilized to facilitate deliveryand/or retrieval of implantable device 10.

FIG. 2 is a perspective view of device 10. Here it can be seen thatdocking member 20 may extend from proximal region 16 of housing 12. Inat least some embodiments, docking member 20 may include a head portion22 and a neck portion 24 extending between housing 12 and head portion22. Head portion 22 may be capable of engaging with a delivery and/orretrieval catheter. For example, if it is desired to retrieve device 10from the patient, a retrieval catheter may be advanced to a positionadjacent to device 10. A retrieval mechanism such as a snare, tether,arm, or other suitable structure may extend from the retrieval catheterand engage head portion 22. When suitably engaged, device 10 may bepulled from the cardiac tissue and, ultimately, removed from thepatient.

The implantable device 10 may include a first electrode 26 positionedadjacent to the distal region 14 of the housing 12. A second electrode28 may also be defined along housing 12. For example, housing 12 mayinclude a conductive material and may be insulated along a portion ofits length. A section along proximal region 16 may be free of insulationso as to define second electrode 28. Electrodes 26/28 may be sensingand/or pacing electrodes to provide electro-therapy and/or sensingcapabilities. First electrode 26 may be capable of being positionedagainst or otherwise contact the cardiac tissue of the heart H whilesecond electrode 28 may be spaced away from the first electrode 26, andthus spaced away from the cardiac tissue.

Device 10 may also include a pulse generator (e.g., electricalcircuitry) and a power source (e.g., a battery) within housing 12 toprovide electrical signals to electrodes 26/28. Electrical communicationbetween pulse generator and electrodes 26/28 may provide electricalstimulation to heart tissue and/or sense a physiological condition.

As the name suggest, anchoring members 18 may be used to anchor device10 to the target tissue. A suitable number of anchoring members 18 maybe used with device 10. For example, device 10 may include one, two,three, four, five, six, seven, eight, or more anchoring members. In atleast some embodiments, anchoring members 18 may take the form ofgrappling hooks that are capable of piercing the cardiac tissue, loopingthrough a portion of the cardiac tissue, and then extending back outfrom the cardiac tissue. In doing so, it may be desirable for anchoringmembers 18 to have relatively shallow penetration into the cardiactissue. In addition, it may be desirable for anchoring members 18 to bearranged so as to be spaced from first electrode 26. Otherconfigurations are contemplated.

In order to achieve these and other goals, anchoring members 18 may havea compound curved structure. For the purposes of this disclosure, acompound curved structure may be understood as a structure that includesa plurality of different curved regions. For example, at least some ofthe anchoring members 18 may include a base region 30, a first curvedregion 32, a generally straight region 34, a second curved region 36,and an end region 38. Base region 30 may be positioned at the junctionbetween anchoring members 18 and housing 12. In some embodiments, baseregion 30 may be fixed to housing 12. In other embodiments, base region30 may be pivotably attached to housing 12. According to theseembodiments, base region 30 may have some freedom of movement relativeto housing 12. In some instance, an actuation mechanism may be coupledto anchoring members 18 so that a clinician may pivot anchoring members18 during an implantation procedure. For example, a translatablemechanical feature such as a wire, tether, or the like may be coupled tohousing 12 that is capable of transmitting motion to anchoring members18.

First curved region 32 may curve away from housing 12. In other words,the curvature of first curved region 32 may result in at least a portionof anchoring members 18 becoming positioned progressively furtherradially away from housing 12. For example, it may be desirable foranchoring members 18 to extend or otherwise be positioned laterally asfar away from first electrode 26 as possible so as to minimize tissueirritation adjacent to where first electrode 26 contacts the wall of theheart. In addition, the curvature of first curved region 32 (and/orother regions of anchoring members 18) may be capable of secured holdingdevice to the wall of the heart while having a relatively shallowpenetration into the tissue. Shallow penetration may help to reducelocal tissue irritation and/or injury of the heart wall.

In some embodiments, the radius of curvature of first curved region 32may be constant. In other embodiments, the radius of curvature may varyalong first curved region 32. For example, first curved region 32 mayinclude a parabolic curve, hyperbolic curve, exponential curve, a curvedefined by a first order polynomial, a curve defined by a second orderpolynomial, a curve defined by a third order polynomial, a curve definedby a fourth order or greater polynomial, etc. First curved region 32 maylie fully within a single plane (e.g., first curved region 32 may extendin only two dimension) or first curved region 32 may lie within morethan one plane (e.g., first curved region 32 may extend in threedimensions). These are just examples. Other curves, shapes,configurations, etc. are contemplated.

Generally straight region 34, as the name suggests, may be substantiallyfree from a curve. Generally straight region 34 may have a suitablelength. For example, in some embodiments it may be desirable for greaterseparation between first curved region 32 and second curved region 36.In such embodiments, it may be desirable for generally straight region34 to have a relatively longer length. In other embodiments, lessseparation may be desired between curved portions 32/36 and, thus,generally straight region 34 may be relatively short. In still otherembodiments, anchoring members 18 may lack generally straight region 34.In other words, first curved region 32 may be directly attached to orotherwise continuous with second curved region 36.

Second curved region 36 may curve toward housing 12. In at least someembodiments, the curvature of second curved region 36 may be oriented inthe opposite direction of first curved region 32. Just like first curvedregion 32, second curved region 36 may have a constant or variableradius of curvature.

End region 38 may be generally straight or end region 38 may include acurve. In at least some embodiments, end region 38 may have a point orrelatively sharpened end that may be capable of penetrating tissue.

In addition to allowing device 10 to be securely anchored to the heartof a patient, anchoring members 18 may also allow for acuterepositioning of device 10. For example, device 10 may be secured to theheart of a patient via anchoring members 18. If it desired to relocatedevice 10, a suitable retrieval and/or repositioning device may be usedto engage device 10 so that it can be repositioned (e.g., removinganchoring members 18 from the tissue and moving device 10 to anotherdesirable location) and re-anchored.

The cross-sectional shape of anchoring members 18 may vary. For example,at least some of anchoring members 18 may have a generally rectangularcross-sectional shape as shown in FIG. 3A. According to theseembodiments, the width W of anchoring member 18 may be greater than thethickness T. However, in other embodiments, the thickness T may begreater than the width W. In other embodiments, at least some ofanchoring members 18 may have a generally circular cross-sectional shapewith a diameter D as depicted in FIG. 3B. Other cross-sectional shapesare contemplated. For example, anchoring members 18 can have an ovalcross-sectional shape (e.g. as depicted in FIG. 3C), a semi-circularcross-sectional shape, a polygonal cross-sectional shape (e.g.,triangular, square, quadrilateral, pentagonal, hexagonal, octagonal,etc.), combinations thereof (e.g., a polymeric shape with rounded edgesor corners), or any other suitable shape. Anchoring members 18 may havethe same cross-sectional shape along essentially the full lengththereof. Alternatively, the cross-sectional shape may vary along thelength of anchoring members 18. For example, portions of anchoringmembers 18 may have a generally non-circular cross-sectional shape andother portions of anchoring members 18 may have a generally circularcross-sectional shape. Furthermore, in some embodiments all of anchoringmembers 18 may have the same cross-sectional shape and/or profile. Inother embodiments, the various anchoring members 18 of a given device 10may differ from one another.

FIG. 4 illustrates a delivery catheter 100 that may be used, forexample, to deliver device 10 to a suitable location within the anatomy(e.g., the heart). Catheter 100 may include a proximal member or region140 and a distal member or holding section 146. A push member 142 may bedisposed (e.g., slidably disposed) within proximal region 140. A headregion 144 of push member 142 may be disposed within distal holdingsection 146. Head region 144 may be capable of engaging docking member20 of device 10. Push member 142 may be used to “push” device 10 outfrom distal holding section 146 so as to deploy and anchor device 10within a target region 148 (e.g., a region of the heart such as theright ventricle). Catheter 100 may be advanced through the vasculatureto target region 148. For example, catheter 100 may be advanced througha femoral vein, into the inferior vena cava, into the right atrium,through the tricuspid valve, and into the right ventricle. Target region148 may be a portion of the right ventricle. For example, target region148 may be a portion of the right ventricle near the apex of the heart.Target region 148 could also be other regions including other regions ofthe heart (e.g., the right atrium, the left ventricle, the left atrium),blood vessel, or other suitable targets.

Anchoring members 18 may be capable of shifting between a firstconfiguration and a second configuration. For example, when device 10 isdisposed within distal holding section 146 of delivery catheter 100,anchoring members 18 may be in the first configuration. When soconfigured, anchoring members 18 may extend distally from device 10 in agenerally more straightened configuration. In other words, anchoringmembers 18 may be oriented in the distal direction. For example,catheter 100 may have a longitudinal axis X and anchoring members 18 maycorresponding longitudinal axis Y that is generally parallel with thelongitudinal axis X of catheter 100. However, anchoring members 18 neednot extend exactly parallel with the longitudinal axis X of catheter 100and, instead, may be generally oriented in the distal direction.

When device 10 is suitably positioned adjacent to target region 148,push member 142 may be distally advanced to push device 10 distally sothat anchoring members 18 engage target region 148. In doing so,anchoring members may shift to the second configuration as shown in FIG.5. When in the second configuration, anchoring members 18 may have thecompound curved configuration. The compound curve of anchoring members18 may help to guide anchoring members 18 away laterally away from thetissue entry point and then back out of the tissue at a location that islaterally spaced from the entry point.

In at least some embodiments, anchoring members 18 may still maintain acompound curvature (e.g., albeit in an altered shape) when in the morestraightened configuration. For example, when device 10 is disposedwithin a delivery catheter, anchoring members 18 may still maintain thecompound curve. In other embodiments, one or more of curves formed inanchoring members 18 may be substantially straightened such thatanchoring members 18 may be considered as no longer having a compoundcurve when in the more straightened configuration. When shifting to thesecond configuration (e.g., which may be considered a deployed,implanted, delivered, or “unbiased” configuration), anchoring members 18may have or otherwise return to a shape that includes the compoundcurve.

When in the first configuration, a portion of anchoring members 18 mayengage an inner wall surface of distal holding section 146. The portionof anchoring member 18 that engages the inner wall surface of distalholding section 146 may be positioned proximally of the distal end ofanchoring member 18. For example, second curved region 36 may engage theinner wall surface of distal holding section 146 as shown in FIG. 4.Other arrangements are contemplated. For example, FIG. 6 illustratesdevice 110 (which may be similar in form and function to other devicesdisclosed herein) including anchoring member 118 and docking member 120.Here it can be seen that first curved region 132 may engage the innerwall surface of distal holding section 146.

FIG. 7 illustrates device 210 (which may be similar in form and functionto other devices disclosed herein) including anchoring member 218 anddocking member 220. In this embodiment, a section of anchoring member218 extending from second curved region 232 to tip 238 may lie flatagainst the inner wall surface of distal holding section 146.

The materials that can be used for the various components of device 10and catheter 100 (and/or other devices/catheters disclosed herein) mayinclude those commonly associated with medical devices. For example,device 10 and/or catheter 100 may be made from a metal, metal alloy,polymer (some examples of which are disclosed below), a metal-polymercomposite, ceramics, combinations thereof, and the like, or othersuitable material. Some examples of suitable polymers may includepolytetrafluoroethylene (PTFE), ethylene tetrafluoroethylene (ETFE),fluorinated ethylene propylene (FEP), polyoxymethylene (POM, forexample, DELRIN® available from DuPont), polyether block ester,polyurethane (for example, Polyurethane 85A), polypropylene (PP),polyvinylchloride (PVC), polyether-ester (for example, ARNITEL®available from DSM Engineering Plastics), ether or ester basedcopolymers (for example, butylene/poly(alkylene ether) phthalate and/orother polyester elastomers such as HYTREL® available from DuPont),polyamide (for example, DURETHAN® available from Bayer or CRISTAMID®available from Elf Atochem), elastomeric polyamides, blockpolyamide/ethers, polyether block amide (PEBA, for example availableunder the trade name PEBAX®), ethylene vinyl acetate copolymers (EVA),silicones, polyethylene (PE), Marlex high-density polyethylene, Marlexlow-density polyethylene, linear low density polyethylene (for exampleREXELL®), polyester, polybutylene terephthalate (PBT), polyethyleneterephthalate (PET), polytrimethylene terephthalate, polyethylenenaphthalate (PEN), polyetheretherketone (PEEK), polyimide (PI),polyetherimide (PEI), polyphenylene sulfide (PPS), polyphenylene oxide(PPO), poly paraphenylene terephthalamide (for example, KEVLAR®),polysulfone, nylon, nylon-12 (such as GRILAMID® available from EMSAmerican Grilon), perfluoro(propyl vinyl ether) (PFA), ethylene vinylalcohol, polyolefin, polystyrene, epoxy, polyvinylidene chloride (PVdC),poly(styrene-b-isobutylene-b-styrene) (for example, SIBS and/or SIBS50A), polycarbonates, ionomers, biocompatible polymers, other suitablematerials, or mixtures, combinations, copolymers thereof, polymer/metalcomposites, and the like. In some embodiments the sheath can be blendedwith a liquid crystal polymer (LCP). For example, the mixture cancontain up to about 6 percent LCP.

Some examples of suitable metals and metal alloys include stainlesssteel, such as 304V, 304L, and 316LV stainless steel; mild steel;nickel-titanium alloy such as linear-elastic and/or super-elasticnitinol; other nickel alloys such as nickel-chromium-molybdenum alloys(e.g., UNS: N06625 such as INCONEL® 625, UNS: N06022 such as HASTELLOY®C-22®, UNS: N10276 such as HASTELLOY® C276®, other HASTELLOY® alloys,and the like), nickel-copper alloys (e.g., UNS: N04400 such as MONEL®400, NICKELVAC® 400, NICORROS® 400, and the like),nickel-cobalt-chromium-molybdenum alloys (e.g., UNS: R30035 such asMP35-N® and the like), nickel-molybdenum alloys (e.g., UNS: N10665 suchas HASTELLOY® ALLOY B2®), other nickel-chromium alloys, othernickel-molybdenum alloys, other nickel-cobalt alloys, other nickel-ironalloys, other nickel-copper alloys, other nickel-tungsten or tungstenalloys, and the like; cobalt-chromium alloys; cobalt-chromium-molybdenumalloys (e.g., UNS: R30003 such as ELGILOY®, PHYNOX®, and the like);platinum enriched stainless steel; titanium; combinations thereof; andthe like; or any other suitable material.

As alluded to herein, within the family of commercially availablenickel-titanium or nitinol alloys, is a category designated “linearelastic” or “non-super-elastic” which, although may be similar inchemistry to conventional shape memory and super elastic varieties, mayexhibit distinct and useful mechanical properties. Linear elastic and/ornon-super-elastic nitinol may be distinguished from super elasticnitinol in that the linear elastic and/or non-super-elastic nitinol doesnot display a substantial “superelastic plateau” or “flag region” in itsstress/strain curve like super elastic nitinol does. Instead, in thelinear elastic and/or non-super-elastic nitinol, as recoverable strainincreases, the stress continues to increase in a substantially linear,or a somewhat, but not necessarily entirely linear relationship untilplastic deformation begins or at least in a relationship that is morelinear that the super elastic plateau and/or flag region that may beseen with super elastic nitinol. Thus, for the purposes of thisdisclosure linear elastic and/or non-super-elastic nitinol may also betermed “substantially” linear elastic and/or non-super-elastic nitinol.

In some cases, linear elastic and/or non-super-elastic nitinol may alsobe distinguishable from super elastic nitinol in that linear elasticand/or non-super-elastic nitinol may accept up to about 2-5% strainwhile remaining substantially elastic (e.g., before plasticallydeforming) whereas super elastic nitinol may accept up to about 8%strain before plastically deforming. Both of these materials can bedistinguished from other linear elastic materials such as stainlesssteel (that can also can be distinguished based on its composition),which may accept only about 0.2 to 0.44 percent strain beforeplastically deforming.

In some embodiments, the linear elastic and/or non-super-elasticnickel-titanium alloy is an alloy that does not show anymartensite/austenite phase changes that are detectable by differentialscanning calorimetry (DSC) and dynamic metal thermal analysis (DMTA)analysis over a large temperature range. For example, in someembodiments, there may be no martensite/austenite phase changesdetectable by DSC and DMTA analysis in the range of about −60 degreesCelsius (° C.) to about 120° C. in the linear elastic and/ornon-super-elastic nickel-titanium alloy. The mechanical bendingproperties of such material may therefore be generally inert to theeffect of temperature over this very broad range of temperature. In someembodiments, the mechanical bending properties of the linear elasticand/or non-super-elastic nickel-titanium alloy at ambient or roomtemperature are substantially the same as the mechanical properties atbody temperature, for example, in that they do not display asuper-elastic plateau and/or flag region. In other words, across a broadtemperature range, the linear elastic and/or non-super-elasticnickel-titanium alloy maintains its linear elastic and/ornon-super-elastic characteristics and/or properties.

In some embodiments, the linear elastic and/or non-super-elasticnickel-titanium alloy may be in the range of about 50 to about 60 weightpercent nickel, with the remainder being essentially titanium. In someembodiments, the composition is in the range of about 54 to about 57weight percent nickel. One example of a suitable nickel-titanium alloyis FHP-NT alloy commercially available from Furukawa Techno Material Co.of Kanagawa, Japan. Some examples of nickel titanium alloys aredisclosed in U.S. Pat. Nos. 5,238,004 and 6,508,803, which areincorporated herein by reference. Other suitable materials may includeULTANIUM™ (available from Neo-Metrics) and GUM METAL™ (available fromToyota). In some other embodiments, a superelastic alloy, for example asuperelastic nitinol can be used to achieve desired properties.

In at least some embodiments, portions or all of device 10 and/orcatheter 100 may also be doped with, made of, or otherwise include aradiopaque material. Radiopaque materials are understood to be materialscapable of producing a relatively bright image on a fluoroscopy screenor another imaging technique during a medical procedure. This relativelybright image aids the user of device 10 and/or catheter 100 indetermining its location. Some examples of radiopaque materials caninclude, but are not limited to, gold, platinum, palladium, tantalum,tungsten alloy, polymer material loaded with a radiopaque filler, andthe like. Additionally, other radiopaque marker bands and/or coils mayalso be incorporated into the design of device 10 and/or catheter 100 toachieve the same result.

In some embodiments, a degree of Magnetic Resonance Imaging (MRI)compatibility is imparted into device 10 and/or catheter 100. Forexample, device 10 and/or catheter 100 (or portions thereof) may be madeof a material that does not substantially distort the image and createsubstantial artifacts (i.e., gaps in the image). Certain ferromagneticmaterials, for example, may not be suitable because they may createartifacts in an MRI image. Device 10 and/or catheter 100 (or portionsthereof) may also be made from a material that the MRI machine canimage. Some materials that exhibit these characteristics include, forexample, tungsten, cobalt-chromium-molybdenum alloys (e.g., UNS: R30003such as ELGILOY®, PHYNOX®, and the like),nickel-cobalt-chromium-molybdenum alloys (e.g., UNS: R30035 such asMP35-N® and the like), nitinol, and the like, and others.

It should be understood that this disclosure is, in many respects, onlyillustrative. Changes may be made in details, particularly in matters ofshape, size, and arrangement of steps without exceeding the scope of thedisclosure. This may include, to the extent that it is appropriate, theuse of any of the features of one example embodiment being used in otherembodiments. The invention's scope is, of course, defined in thelanguage in which the appended claims are expressed.

What is claimed is:
 1. An implantable leadless pacing device,comprising: a pacing capsule including a housing, the housing having aproximal region and a distal region; a first electrode disposed alongthe distal region; and one or more anchoring members coupled to thedistal region, the anchoring members each including a region with acompound curve.
 2. The implantable leadless pacing device of claim 1,wherein the region with the compound curve includes a first curvedsection and a second curved section.
 3. The implantable leadless pacingdevice of claim 2, wherein the first curved section is oriented in afirst direction and wherein the second curved section is oriented in asecond direction different from the first direction.
 4. The implantableleadless pacing device of claim 3, wherein the first direction isopposite the second direction.
 5. The implantable leadless pacing deviceof claim 2, wherein a straight region is disposed between the firstcurved section and the second curved section.
 6. The implantableleadless pacing device of claim 2, wherein each of the one or moreanchoring members include a pointed tip section.
 7. The implantableleadless pacing device of claim 2, wherein the first curved section, thesecond curved section or both are capable of causing the one or moreanchoring members to move laterally away from the first electrode whenthe one or more anchoring members extend within a target tissue.
 8. Theimplantable leadless pacing device of claim 2, wherein the first curvedsection, the second curved section or both have a radius of curvaturethat varies.
 9. The implantable leadless pacing device of claim 1,wherein each of the anchoring members are capable of shifting between afirst configuration and a deployed configuration, and wherein each ofthe anchoring members include the region with the compound curve when inthe deployed configuration.
 10. An implantable leadless pacing devicesystem, the system comprising: a delivery catheter having a proximalsection, a distal holding section, and a lumen formed therein; a pushmember slidably disposed within the lumen; a leadless pacing deviceslidably received within the distal holding section, the leadless pacingdevice comprising: a housing having a proximal region and a distalregion, a first electrode disposed along the distal region, and aplurality of anchoring members including a first anchoring membercoupled to the distal region; wherein the first anchoring member iscapable of shifting between a first configuration when the leadlesspacing device is disposed within the distal holding section and a secondconfiguration when the leadless pacing device is advanced out from thedistal holding section; wherein the distal holding section has alongitudinal axis; wherein the first anchoring member is arrangedsubstantially parallel with the longitudinal axis when the firstanchoring member is in the first configuration; and wherein the firstanchoring member includes a region with a compound curve when the firstanchoring member is in the second configuration.
 11. The system of claim10, wherein the region with the compound curve includes a first curvedsection and a second curved section.
 12. The system of claim 11, whereinthe first curved section is oriented in a first direction and whereinthe second curved section is oriented in a second direction differentfrom the first direction.
 13. The system of claim 12, wherein the firstdirection is opposite the second direction.
 14. The system of claim 11,wherein a contact section of the first anchoring member contacts aninner wall surface of the distal holding section when the firstanchoring member is in the first configuration.
 15. The system of claim14, wherein the contact section is positioned proximal of a distal endof the first anchoring member.
 16. The system of claim 15, wherein thecontact section extends between the distal end of the first anchoringmember and a point disposed proximal of the distal end.
 17. The systemof claim 11, wherein the first curved section, the second curved sectionor both are capable of causing the first anchoring member to movelaterally away from the first electrode when the first anchoring memberextends within a cardiac tissue.
 18. An implantable leadless pacingdevice system, the system comprising: a delivery catheter having aproximal section, a distal holding section, and a lumen formed therein;a push member slidably disposed within the lumen; a leadless pacingdevice slidably received within the distal holding section, the leadlesspacing device comprising: a housing having a proximal region and adistal region, a first electrode disposed along the distal region, and aplurality of anchoring members including a first anchoring membercoupled to the distal region; wherein the first anchoring member iscapable of shifting between a first configuration when the leadlesspacing device is disposed within the distal holding section and a secondconfiguration when the leadless pacing device is advanced out from thedistal holding section; wherein a contact section of the first anchoringmember contacts an inner wall surface of the distal holding section whenthe first anchoring member is in the first configuration; wherein thecontact section is positioned proximally of a distal end of the firstanchoring member; and wherein the first anchoring member includes aregion with a compound curve when the first anchoring member is in thesecond configuration.
 19. The system of claim 18, wherein the regionwith the compound curve includes a first curved section and a secondcurved section.
 20. The system of claim 19, wherein the first curvedsection is oriented in a first direction and wherein the second curvedsection is oriented in a second direction different from the firstdirection.